Features1 Mounting orientation, for simple mounting in approximately 4-5 secondsInternal taper surface locks in place with interfacing barrel adapters and drastically reduces or eliminates common baffle/end cap strikes Compatible with Universal QD pistons barrel adapters (sold separately)Total system weight is identical to legacy direct thread pistonsH900 heat treated for improved durability and wear resistance17-4 stainless steel materialQPQ Nitride finish for attractive, durable black finish Note: 1/2"x28 special is intended for tilt barrel compact 9mm pistols which generally have smaller outside diameter barrels and thus no typical thread shoulder. Examples are : Sig P365, Glock 43. Glock 48... etc. Users with mid to full size handguns should choose the standard 1/2"x28 size